triskaidekaphobia

Irrational fear of things or events associated with the number 13.

The number 13 is
considered especially unfavorable though it was considered a lucky number in
ancient Egypt and China. There were 13 people at the Last Supper. And
several mass murderers have 13 letters in their names: Charles Manson,
Jeffrey Dahmer, Theodore Bundy. Of course, millions of people who haven't
committed any murders, such as Richard Cheney and Robert Redford, have 13 letters in their
names, too. As far as I know, nobody has studied how many dinner parties
with 13 present went off uneventfully. Witches, perhaps to clearly oppose
themselves to a Christian superstition, sometimes have groups of 13 known
as covens.

Some think 13 owes its bad reputation to Loki, the
Norse god of evil, who started a riot when he crashed a banquet at
Valhalla attended by 12 gods.

Some cities skip 13th Ave., but not Sacramento,
which has an intersection where 13th Street crosses
13th Avenue. Some buildings skip from the
12th to the 14th floor, which, of course, means that the 14th floor is
actually the 13th floor.

The ancient Egyptians considered the 13th stage
of life to be death, i.e., the afterlife, which they thought was a good
thing. The Death card in a tarot deck is numbered
13 and represents transformation. Those cultures with lunar calendars and
13 months don't associate 13 with anything sinister.

According to a 1996 Gallup poll, 9 percent of Americans
are superstitious about the number 13.